Gold miner Randgold Resources has said operations at its three projects in Mali are running normally despite reports of a coup, while other mining groups are monitoring the situation.

A military group said it had seized power and imposed a curfew in the west African state, and the whereabouts of the president, Amadou Toumani Touré, were unclear. Randgold, which is one of the top 100 companies listed on the London Stock Exchange, has around 70% of its production in Mali, and is expected to mine around 600,0000 ounces of gold there this year.

Its chief executive, Mark Bristow, is in Mali and this week signed an agreement over its Gounkoto mine with Amadou Cissé, the mining minister.

On the stock market Randgold's shares have lost nearly 12%, wiping nearly £700m off its value. Joshua Raymond, chief market strategist at City Index, said: "Investors hate uncertainty and with the country in a state of emergency we have seen significant reductions in investors' positions in Randgold Resources. This could continue until there is a sense of clarity surrounding the situation within the country."

Other miners in the country include AngloGold, Gold Fields, IAMGold, and Cluff Gold. AngloGold also said its operations were not currently affected.